How many types of indexes are there in sql server?

In SQL Server, there are primarily seven types of indexes:

1. Clustered Index: This type of index sorts and stores the data rows in the table or view based on their key values. There can only be one clustered index per table.

2. Non-Clustered Index: A non-clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. A table can have multiple non-clustered indexes.

3. Unique Index: This type of index ensures that the index key contains only unique values to enforce the uniqueness of key values in a table or view.

4. Filtered Index: A filtered index is an optimized non-clustered index, especially suited to cover queries that select from a well-defined subset of data.

5. Full-Text Index: This type of index is used by Full-Text Search. It enables SQL Server to perform sophisticated searches on text data.

6. Spatial Index: This type of index is used to optimize queries that perform operations on spatial objects.

7. XML Index: This type of index is used to optimize queries on XML data.

Each type of index serves a different purpose and can be used in different scenarios to optimize the performance of a database.